1. Field of the Invention
The present invention relates to an endoscope apparatus and, more particularly, to an endoscope apparatus that acquires image signals through laser light scanning
2. Description of the Related Art
As is well-known, electronic endoscopes are used that carry out photoelectric conversion of a subject image by employing an image pickup apparatus including a solid-state image pickup device such as a CCD and CMOS and displays an acquired image on a monitor. In recent years, scanning endoscope apparatuses have been used for displaying a subject image, without employing the technology of the solid-state image pickup device. The scanning endoscope apparatus scans a subject with a distal end of an illumination fiber that guides light from a light source, receives return light from the subject with an optical fiber bundle disposed around the illumination fiber, and generates a subject image by using chronologically detected light intensity signals.
For example, Japanese Patent Application Laid-Open Publication No. 2011-19706 discloses a medical observation system including a scanning medical probe that transmits laser light from a laser light source to a distal end portion of an insertion portion via a single-mode optical fiber and irradiates the subject.
The medical observation system disclosed in Japanese Patent Application Laid-Open Publication No. 2011-19706 has an optical fiber inserted through and fixed in a through hole of an actuator formed with a piezoelectric device or the like and supplies a driving voltage to a plurality of electrodes provided to the actuator in XY-axis direction to cause the optical fiber to vibrate in a predetermined manner and scan the laser light.
FIG. 9A is a view for illustrating a state of propagation of a laser light in conventional arts.
As shown in FIG. 9A, a conventional scanning endoscope apparatus drives an actuator 100 to vibrate (double-pointed arrow 102) an optical fiber 101. The laser light emitted from the optical fiber 101 is concentrated, for example, at a focal point 105 by lenses 103, 104 constituting a distal end optical system. The vibration (double-pointed arrow 102) of the optical fiber 101 also causes the focal point 105 to vibrate (double-pointed arrow 106), thereby allowing to scan a living body with the laser light.
FIG. 9B is a view for illustrating a state of propagation of a laser light when the optical fiber is broken in conventional arts. As shown in FIG. 9B, when a part of the optical fiber 101 is broken which is on a distal end side with respect to the actuator 100, almost no amplitude (double-pointed arrow 102a) of the optical fiber 101 can be acquired.